In various signal processing applications, programmable gain control plays an important role for overall system performance. In one known gain control approach, a digital code is converted to a current source by a delta-sigma digital-to-analog converter (delta sigma DAC). An amplifier in a non-inverting feedback configuration converts the current to a voltage at an output of the amplifier using voltage division with resistors around an amplifier feedback loop. In such an approach, large resistors and their associated metal interconnect can introduce large parasitic reactive components (e.g., capacitance) at the non-inverting node of the amplifier and can add to circuit delay and make amplifier compensation more difficult, e.g., over a wide range of gain and frequency.
In another known approach, digital gain programming is used, e.g., in audio applications, to control volume by numerically adjusting the signal amplitude in the digital domain. Digital volume reduction using various techniques results in fewer bits being available to represent an audio signal, while retaining the same noise level. This reduces the signal to noise ratio (SNR) or the dynamic range of the entire signal processing chain. In other words, the resolution of the audio signal is degraded by the noise floor when digital gain programming is used.